The present invention relates to a device for producing a green compact from a powdered or granular material as well as a method for producing a green compact from a powdered or granular material.
Known processing tools like drill bits and circular saw blades are made of a main body which is connected to cutting segments. The cutting segments are connected to the main body by laser welding, for example, and are made of a base zone and a use zone. The area of the cutting segment that is connected to the main body of the processing tool is designated as the base zone and the remaining cutting segment as the use zone. The base zone is made of, for example, a weldable material so the main body and the cutting segments are able to be welded together well. The use zone is made of a basic material and cutting particles that are embedded into the basic material. The cutting particles are designed as diamond particles or other abrasive particles, which are suitable for abrasive processing. The cutting effect is produced by the cutting particles and the basic material serves to fix the cutting particles.
The cutting segments are produced in a two-stage method from powdered or granular materials. In a first stage, a green compact is constructed of material layers lying on top of one another and in a second stage, the green compact is finished in a sintering plant by the effect of temperature and/or pressure. In a first group of manufacturing methods the cutting particles are mixed into the basic material and distributed uniformly in the basic material. The disadvantage is that it is possible for cutting particle nests to form, which reduce the cutting efficiency and the service life of the cutting segments. In a second group of manufacturing methods, the basic material is applied layer-by-layer with a fill shoe and the cutting particles are placed in the basic material by a placing unit in a separate placement step. Because of the separate placement step, it is possible to vary the concentration and distribution of the cutting particles in the material layer and adapt them to the processing task.
Known devices for producing a green compact from a powdered or granular material by successive application and compression of the material are comprised of a fill shoe, which is filled with the material or several materials and is designed to be adjustable by means of an adjusting device, a matrix having at least one construction chamber, which the fill shoe fills layer-by-layer with the material, and a press having a lower punch and an upper punch, which are adjustable by means of a height adjustment device and which compress the material applied layer-by-layer in the construction chamber. A first park position is provided for the fill shoe, in which the fill shoe is disposed during the pressing process. To fill the construction chamber with material, the fill shoe is moved out of the park position into an end position, in which the fill shoe is opened and begins filling the material into the construction chamber. At the end of the filling process, the fill shoe is closed. This position is designated as the second end position for the fill shoe. After the filling process, the fill shoe is moved back out of the second end position over the first end position into the park position.
During the forward movement of the fill shoe between the first and second end positions and during the return movement between the second and first end positions, a one-sided compression of the material is produced on the edge of the construction chamber. The one-sided compression of the material leads to irregularities in the material density. These irregularities may reduce the cutting efficiency and the service life of the cutting segments.
In order to reduce the problem of one-sided compression during the filling process, vibrating the matrix and/or the fill shoe using shaking movements or oscillations during the filling process is known. The shaking movements or oscillations produce a uniform distribution of the material in the construction chamber. However, it is problematic that the cutting particles are likewise distributed uniformly in the material layer and are no longer in the position predetermined by the placing unit in the placement step.
As an alternative, the fill shoe may be moved in different directions of movement over the matrix or over the construction chambers in order to reduce one-sided compression. The problem with this solution is that the movements increase the complexity of the machine and additional machine components are required.
The object of the present invention is further developing a device and a method for producing a green compact from a powdered or granular material by layer-by-layer application and compression of the material to the effect that the cutting segments have a uniform material density without additional machine components. In addition, the required time for constructing the green compacts is reduced.
This object is attained by the device cited at the outset for producing a green compact from a powdered or granular material according to the invention and by the method cited at the outset for producing a green compact from a powdered or granular material according to the invention. Advantageous further developments are disclosed in the dependent claims.
In the case of the device cited at the outset, the invention provides for a second park position to be provided for the fill shoe, wherein the second park position is different from the first park position. Because a second park position is provided for the fill shoe, it is possible to maintain the direction of movement of the fill shoe after the filling process. The fill shoe does not have to be decelerated first and then accelerated in the opposite direction of movement. If the fill shoe were to be moved back into its park position after the filling process, it would also have to cover the distance over the matrix. In addition, the direction of movement in which the material is applied may be reversed in successive material layers without requiring a second fill shoe.
In a preferred embodiment, the fill shoe can be connected in the first and/or second park position to a filling station, which fills the fill shoe with material. The auxiliary process time, during which the fill shoe is disposed in a park position, is utilized to fill the fill shoe with material. Because of the filling station, it is possible to design the fill shoe to be smaller since the fill shoe may be filled regularly with material. If a filling station is not provided for the fill shoe, the fill shoe must be filled with a greater quantity of material or be connected via supply lines to a storage tank. Because of the movement of the fill shoe it is possible for the supply lines to disconnect thereby interfering with or interrupting the supply of material.
It is especially preferred that the fill shoe can be connected to a first filling station in the first park position and to a second filling station in the second park position. Because of the second filling station, it is possible to better utilize the auxiliary process time during which the fill shoe is disposed in a park position.
In a first preferred variant, a first material can be filled at the first filling station and a second material at the second filling station. The filling system is designed to be structurally simpler because only one material is filled at each filling station. Each filling station only has to be connected via one supply line to the storage tank.
In a second preferred variant, a first and second material can be filled at the first and second filling station. The lower the amount of material that must be present in the fill shoe, the smaller and therefore compacter the fill shoe may be. If all materials are able to be filled at both filling stations, it suffices if the fill shoe contains material to apply one material layer.
The speed of the fill shoe is preferably adjustable via the adjusting device. The adjustability of the speed at which the fill shoe moves may be utilized to increase the speed during positioning of the fill shoe as compared to a constant travel speed between the first and second end positions of the filling process. Higher speeds during positioning may reduce the auxiliary process times when constructing the green compacts.
In doing so, the adjusting device of the fill shoe is especially preferably designed as an electric motor. The speed at which the fill shoe is moved over the work surface is adjustable via a control device. In order to reduce the auxiliary process times when constructing the green compacts, the fill shoe is moved at a higher speed than during the filling process from a park position into an end position or from an end position into a park position. The travel speed during the filling process depends above all on the filling behavior of the material.
In the case of the method cited at the outset, the invention provides for the fill shoe to be moved from the second end position into a second park position after application of the material, wherein the second park position is different from the first park position. The positioning path of the fill shoe is reduced, because the fill shoe is moved into the second park position after the filling process. If the fill shoe were to be moved back into its park position after the filling process, it would also have to cover the distance over the matrix.
The material is preferably applied in one material layer in a first direction of movement and in a subsequent further material layer in a second direction of movement, wherein the first and second directions of movement are opposed to one another. Due to the feed movement, a compression zone with increased material density develops during the filling process in the end region of the material layer. The fact that the direction of movement is reversed after every material layer does not compound the errors, but counteracts them.
The speed at which the fill shoe is moved between the park position and the end position is preferably increased at least in sections as compared to a constant speed of the fill shoe between the end positions. Higher speeds during positioning of the fill shoe may reduce the auxiliary process times when constructing the green compacts and therefore the time required to construct the green compacts.
Exemplary embodiments of the invention are described in the following on the basis of the drawings. These drawings are not necessarily supposed to represent the exemplary embodiments to scale; rather the drawings are executed in a schematic and/or slightly distorted form when it is useful for explanatory purposes. Reference is made to the pertinent prior art with respect to additions to the teachings directly identifiable from the drawings. It must be taken into consideration in this case that a wide range of modifications and changes related to the form and detail of an embodiment may be undertaken without deviating from the general idea of the invention. The features of the invention disclosed in the description, the drawings as well as in the claims may be essential for the further development of the invention both separately as well as in any combination. Moreover, all combinations of at least two features disclosed in the description, the drawings and/or the claims fall within the scope of the invention. The general idea of the invention is not restricted to the exact form or detail of the preferred embodiment described and depicted in the following or restricted to a subject matter which would be limited as compared to the subject matter claimed in the claims. In the case of any dimensioning ranges given, values within the stated limits are also meant to be disclosed as limit values, and be applicable at will and claimable. For the sake of simplicity, the same reference numbers are used in the following for identical or similar parts having an identical or similar function.